I have always been taught that indirect questions are written as such:
Rettulit mihi quid accidisset. Indirect questions are formed where the main part of the sentence, in this case to relate, is in the indicative, followed by the question word (what), and ending with the verb making up the question in the subjunctive. Let me make this more clear with another example:
Rogavisti me cur per noctem ambularem.
You asked me why I was walking during the night.
Rogavisti the main verb, is in the indicative, while ambularem, the indirect question verb, is in the subjunctive but still translated as indicative. The subjunctive tense you use should match that of the indicative it is being translated as.
So, according to my education, neither of your options are correct. But, I have read somewhere that the indicative can still be used instead of the subjunctive. In this case it would then be Rettulit mihi quid acciderat. I'm sure you could bend it to make it relative, but I would advise against it, as it somewhat distorts the meaning when there are already good options that preserve the meaning. Thus, verbs don't really have "preferences."
If I didn't explain it very well, I found this site that does a nice job with great examples.